Hi Priscilla,

     For trichrome, mucin, and PAS a small piece of colon or small intestine should be sufficicient.  For H. Pylori we do  cut extra slides from known positive cases. For all others (mainly immuno-related), our pathologists are very good at letting us know when they have a positive case with tissue left that has not been submitted for micro. This way you don't compromise the patient's blocks. It's good to remember with immuno that purchased controls do not reflect the same fixation and processing as in-house tissue, therefore a titration based on them may not adequately demonstrate staining on your own blocks. Hope this helps!

Chris from Chicago